[RFC PATCH v1 13/25] unwind_user/eh_frame: Show file name in debug output

[Jens Remus <jremus@linux.ibm.com>]

When debugging eh_frame issues, the error messages aren't all that helpful
without knowing what file a corresponding .eh_frame[_hdr] section belongs
to.  Prefix debug output strings with the file name.

Based on Josh Poimboeuf's, Steven Rostedt's, and my unwind user sframe
implementation.

Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
 include/linux/eh_frame.h       |  4 ++++
 kernel/unwind/eh_frame.c       | 13 ++++++++----
 kernel/unwind/eh_frame_debug.h | 37 ++++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/include/linux/eh_frame.h b/include/linux/eh_frame.h
index e33041e4f9c0..b2f98cd6166f 100644
--- a/include/linux/eh_frame.h
+++ b/include/linux/eh_frame.h
@@ -11,6 +11,10 @@
 struct eh_frame_section {
 	struct rcu_head	rcu;
 
+#ifdef CONFIG_DYNAMIC_DEBUG
+	const char	*filename;
+#endif
+
 	unsigned long	eh_frame_hdr_start;
 	unsigned long	eh_frame_hdr_end;
 	unsigned long	text_start;
diff --git a/kernel/unwind/eh_frame.c b/kernel/unwind/eh_frame.c
index 7657291324c0..46ffb535ca53 100644
--- a/kernel/unwind/eh_frame.c
+++ b/kernel/unwind/eh_frame.c
@@ -1154,15 +1154,18 @@ int eh_frame_find(unsigned long ip, struct unwind_user_frame *frame)
 	 * e.g. EINVAL (corrupted) or EFAULT (inaccessible).
 	 * Keep if ENOENT (not found) or EOPNOTSUPP (unsupported CFI).
 	 */
-	if (ret && (ret != -ENOENT && ret != -EOPNOTSUPP))
+	if (ret && (ret != -ENOENT && ret != -EOPNOTSUPP)) {
+		dbg_sec("removing bad .eh_frame[_hdr] section\n");
 		if (eh_frame_remove_section(sec->eh_frame_hdr_start))
 			dbg("eh_frame_remove_section() failed\n");
+	}
 
 	return ret;
 }
 
 static void free_section(struct eh_frame_section *sec)
 {
+	dbg_free(sec);
 	kfree(sec);
 }
 
@@ -1290,6 +1293,8 @@ int eh_frame_add_section(unsigned long eh_frame_hdr_start,
 	sec->text_start		= text_start;
 	sec->text_end		= text_end;
 
+	dbg_init(sec);
+
 	ret = eh_frame_read_header(sec);
 	if (ret)
 		goto err_free;
@@ -1297,8 +1302,8 @@ int eh_frame_add_section(unsigned long eh_frame_hdr_start,
 	ret = mtree_insert_range(eh_frame_mt, sec->text_start, sec->text_end - 1,
 				 sec, GFP_KERNEL_ACCOUNT);
 	if (ret) {
-		dbg("mtree_insert_range failed: text=%lx-%lx\n",
-		    sec->text_start, sec->text_end);
+		dbg_sec("mtree_insert_range failed: text=%lx-%lx\n",
+			sec->text_start, sec->text_end);
 		goto err_free;
 	}
 
@@ -1320,7 +1325,7 @@ static int __eh_frame_remove_section(struct mm_struct *mm,
 				     struct eh_frame_section *sec)
 {
 	if (!mtree_erase(&mm->eh_frame_mt, sec->text_start)) {
-		dbg("mtree_erase failed: text=%lx\n", sec->text_start);
+		dbg_sec("mtree_erase failed: text=%lx\n", sec->text_start);
 		return -EINVAL;
 	}
 
diff --git a/kernel/unwind/eh_frame_debug.h b/kernel/unwind/eh_frame_debug.h
index 5a3e4e7f065a..40a80861d4d4 100644
--- a/kernel/unwind/eh_frame_debug.h
+++ b/kernel/unwind/eh_frame_debug.h
@@ -3,6 +3,7 @@
 #define _EH_FRAME_DEBUG_H
 
 #include <linux/eh_frame.h>
+#include <linux/mm.h>
 #include "eh_frame.h"
 
 #ifdef CONFIG_DYNAMIC_DEBUG
@@ -10,9 +11,45 @@
 #define dbg(fmt, ...)							\
 	pr_debug("%s (%d): " fmt, current->comm, current->pid, ##__VA_ARGS__)
 
+#define dbg_sec(fmt, ...)						\
+	dbg("%s: " fmt, sec->filename, ##__VA_ARGS__)
+
+static inline void dbg_init(struct eh_frame_section *sec)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	const char *name;
+
+	guard(mmap_read_lock)(mm);
+	vma = vma_lookup(mm, sec->eh_frame_hdr_start);
+	if (!vma)
+		sec->filename = kstrdup("(vma gone???)", GFP_KERNEL_ACCOUNT);
+	else if (vma_is_anonymous(vma))
+		 sec->filename = kstrdup("(anonymous)", GFP_KERNEL_ACCOUNT);
+	else if (vma->vm_file)
+		sec->filename = kstrdup_quotable_file(vma->vm_file, GFP_KERNEL_ACCOUNT);
+	else if (vma->vm_ops && vma->vm_ops->name && (name = vma->vm_ops->name(vma)))
+		sec->filename = kstrdup(name, GFP_KERNEL_ACCOUNT);
+	else if (arch_vma_name(vma))
+		sec->filename = kstrdup(arch_vma_name(vma), GFP_KERNEL_ACCOUNT);
+	else if (!vma->vm_mm)
+		sec->filename = kstrdup("(vdso)", GFP_KERNEL_ACCOUNT);
+	else
+		sec->filename = kstrdup("(vma unknown???)", GFP_KERNEL_ACCOUNT);
+}
+
+static inline void dbg_free(struct eh_frame_section *sec)
+{
+	kfree(sec->filename);
+}
+
 #else /* !CONFIG_DYNAMIC_DEBUG */
 
 #define dbg(args...)			no_printk(args)
+#define dbg_sec(args...)		no_printk(args)
+
+static inline void dbg_init(struct eh_frame_section *sec) {}
+static inline void dbg_free(struct eh_frame_section *sec) {}
 
 #endif /* !CONFIG_DYNAMIC_DEBUG */
 
-- 
2.53.0